The invention relates to power conversion apparatus and methods, and more particularly, to uninterruptible power supplies (UPSs) and methods of operation thereof.
Power supply circuits are commonly used in equipment such as UPSs, motor drives, and other applications. Conventional UPSs use a variety of different circuit topologies, including standby, line-interactive and on-line topologies. Generally, each of these topologies has advantages and disadvantages and, accordingly, selection of a particular topology is typically governed by the needs of the application.
A common feature of many types of UPSs is the use of a transfer switch that is operative to transfer the load at the output of the UPS between the AC utility and a converter circuit, e.g., an inverter, cycloconverter, etc., that can supply AC power to the load. Such transfer switches may be referred to using various names, such as “static switch” or “bypass switch,” generally depending on the nature of the UPS involved. In many conventional UPSs, such transfer switches are implemented using thyristor circuits, typically antiparallel connected silicon controlled rectifiers (SCRs).